#
# The MIT License (MIT)
#
# Copyright (c) 2018-2020 azai/Rgveda/GolemQuant
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
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# copies or substantial portions of the Software.
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
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# SOFTWARE.
#

# 定义一个常量类实现常量的功能
# 
# 该类定义了一个方法__setattr()__,和一个异常ConstError, ConstError类继承 
# 自类TypeError. 通过调用类自带的字典__dict__, 判断定义的常量是否包含在字典 
# 中。如果字典中包含此变量，将抛出异常，否则，给新创建的常量赋值。 
# 最后两行代码的作用是把const类注册到sys.modules这个全局字典中。
class _const:
    class ConstError(TypeError):pass
    def __setattr__(self,name,value):
        if name in self.__dict__:
            raise self.ConstError("Can't rebind const (%s)" %name)
        if not name.isupper():
            raise self.ConstCaseError("const name '%s' is not all uppercase" % name)

        self.__dict__[name] = value

#import sys
#sys.modules[__name__] = _const()
